Tom,I was wondering what results you got from running this. I have been running it for a weak and was hopping to compare results. Tho my Po4 is not that high .05 my goal was to maintain my present level.I used1/2 cup in each reactor. I run two brs dual reactors. I just tested my Po4 and am glad to report a .04. I have seen no negative sighn of useing this product. It tumbles very well in the reactor and am hopping this level maintains itself. I do not strive for all zero's like many reefers. Small trace elements is what I am looking for ! I did some reading on several others forums in their chemistry forums to see if anyone else was useing it or had negative results or bad experience to report and I really didn't read anything negative about it other then AZ's input. Looking forward to your results.